FIG. 1 illustrates a conventional television power switch, comprising a microcomputer 10 for generating predetermined control signals and a transistor Q1 that is turned on or off by the control signals fed from the microprocessor. A relay RL supplies and cuts off the AC power to each operating section of the television set in accordance with the on or off state of the transistor Q1.
When a user turns on a power switch button (not shown) attached to the housing of the television set, the microcomputer 10 recognizes this and generates a high level signal. This high level signal is applied to the base of the transistor Q1, thereby turning on the transistor Q1. When the transistor Q1 is turned on, a current of more than a predetermined magnitude flows through the relay RL, thereby connecting the two contact points of the relay switch SW. This connection causes AC power to be supplied to each operating section of the television set. The relay RL operates such that when a current of more than a predetermined magnitude (approximately 80 mA) flows through the coil of the relay RL, the relay switch SW is connected and voltage is supplied through the power plug to each operating section. On the other hand, when a current under the predetermined magnitude flows through the coil of the relay, the relay switch SW is cut off.
More specifically, when the transistor Q1 is turned on by a high level control signal generated by the microcomputer 10, a current flows to the coil of the relay from a voltage source Vcc coupled to one end terminal of the coil of the relay RL, thereby connecting the switch SW, so that the AC power is supplied to each operating section. On the other hand, when a low level control signal is applied to a base terminal of the transistor Q1 and the transistor Q1 is turned off, the current does not flow to the coil of the relay RL. Accordingly, the switch SW is turned off and the AC power supply is cut off.
Thus, the conventional power switch only supplies or cuts off the power voltage applied from outside when a user turns on or off the power of the television set. In accordance with the television set provided with this conventional power switch, a predetermined picture transient phenomenon appears when the power is turned off. The picture transient phenomenon represents a particular color that instantaneously stands out in bold relief and is displayed on the screen when the set is turned off. The transient phenomenon may also represent an afterglow like a spark that remains on the screen and then disappears at the moment that the power is turned off. This picture transient phenomenon occurs because a video signal is instantaneously output even though the power supplied to the display section is cut off. This instantaneous power output causes the electron beam to be scattered by the cut off power when the power is turned off. Accordingly, the conventional television power switch only turns ON and OFF the outside power that is applied to each operating section. Thus, the power is cut off while the system is in a TV signal mode whereby a chroma IC outputs a TV video signal. Accordingly, the TV video signal output from the chroma IC is abnormally deflected when the external power is turned off, thereby producing the picture transient phenomenon.